The measurement of red cell lifespan using 59Fe

Red cell lifespan has been measured using 51Cr and 59Fe in 19 patients. 59Fe can be used to give results which agree closely with those obtained using 51Cr provided that the plasma 59Fe clearance curve is properly defined and the data analysed correctly. In some patients elution of 51Cr may be more than three times the normal level and the use of 59Fe may provide the only reliable estimate of red cell lifespan.